Also worth to point out Earth needed millions of years to sequester that CO2 we release to atmosphere each year.
- The fossil fuels burned in a year represent about 400 years' worth of accumulated ancient biomass. That is, you'd need to capture all the biomass grown for four centuries to give the fuel we consume in one year.
- But conversion and preservation aren't perfect. So it took five million years to form just the oil we consume annually (or did in 1997, though values have remained reasonably constant since). That is, only about 0.008% of ancient biomass was stored as petroleum.
I don't know the figures for carbon-cycle sequester and release rates, though at best we're looking at centuries to remove what we've put into the atmosphere in decades, if not longer.
Coal/oil deposits that we are using up now formed because at the time there was no bacteria that could digest dead plant/plankton matter.
This is also why all coal/oil deposits are very old. There is very little deposits after bacteria has evolved.
Nowadays there needs to be special circumstances for a piece of biological matter to not be digested by bacteria. For example it would have to be covered by permafrost or drown in oxygen-deficient lake for a very, very long time and then covered by soil.
I think energy is least of problems. At the beginning forests provide a lot of energy and would be enough to bridge to industrial times (at least for us).
The real issue, I think, is lack of easily available raw materials like iron, tin, copper, etc. We have depended A LOT on iron practically lying on the ground.
Without having some iron easily available any startup civilization wouldn't know to look deeper and even if they wanted, they would not have any tools to do so.
At least with energy there is multiple ways to acquire it.
https://en.wikipedia.org/wiki/Ore_genesis
Useful ore deposits tend to be vast, with absoutely immense amounts (many trillions tons) of paydirt. The value of ores are that the minerals of interest are concentrated, sometimes to very high levels (50% or more of total material), though increasingly lower-grade ores (1% concentration or lower) are utilised. This means that you've got to move 99 units of mass for every unit of primary mineral extracted (overburden).
Even very large human formations are small by geological standards. The World Trade Centre towers contained about 200,000 tonnes of steel. That's a lot for humans, but a minuscule amount on a geological scale. (https://hypertextbook.com/facts/2004/EricChen.shtml)
Current iron ore extraction is on the order of about 2.5 billion tons/year. That's roughly 1/3 ton per person on Earth.
https://www.visualcapitalist.com/all-the-worlds-metals-and-m...
Vaclav Smil's Making the Modern World goes into depth on material use in contemporary civilisation:
https://www.worldcat.org/title/making-the-modern-world-mater...
(After water and oil, sand and gravel are our most-used material, then concrete and iron/steel.)
Then there’s the question of how much of the steel will still be usable when it’s time to extract it. That’s a variable problem depending on how long the ‘dark age’ is before people are rebuilding I suppose. It could be like Doctorow’s Walkaway where there’s abundant enough discarded resources you can almost achieve post-scarcity (but that world never wen through a hard crash it was more building a parallel society than a whole new one). Or it could be centuries later when a lot of the steel will be rust. Hard to say.
This roughly suggests to me, for whatever reason, there is no longer circumstances for new deposits to form.
A problem with just spreading this out on beaches and the like is that these rocks are also often enriched in nickel vs. the average crustal rock, and this would release many millions of tonnes of nickel into the environment. There is some evidence that nickel release was part of the terrible events at the Permian-Triassic extinction. Nickel is crucial to the enzymes in the metabolic pathways leading to the production of methane in anaerobic environments. There's an idea that nickel injection into the oceans by fallout from the PT megaeruption in Siberia led to massive methane production.
This is (mostly) a non-sequitur to any modern discussion about climate, the atmosphere, and its effects on human life and civilization.
Life, at this point is used to a particular equilibrium. Sure, life has existed at different equilibriums. But we also know when those equilibriums are massively disturbed (via a great oxygenation event, massive asteroid, major volcanic eruptions, etc.) much of the life dies out (obviously depends on the intensity of the disruption) and it takes many years for life to adjust to and make a new equilibrium.
Humanity should be deeply concerned with how deeply we have disrupted the equilibrium, as this disrupts the world and biosphere that sustains us.
It might be useful if you're building an argument that humanity will be better off after the current mass extinction event is over. However, I tend to find this point more often leads to a George Carlin-esque cynicism and nihilism about earth being better off without humans (or human civilization) anyways.
“Carbon dioxide concentrations have varied widely over the Earth's 4.54 billion year history.”:
https://en.m.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_...
Sequestering is a process where carbon becomes unavailable for biological processes.
So you have carbon circulating (present in biomass, returned to atmosphere, then back to biomass, etc.) and you have carbon that is not available for circulation.
Carbon in atmosphere is part of circulation. When a supervolcano erupts and emits a bunch of CO2, this adds carbon to atmosphere but then that carbon may very quickly be bound in biomass (for example algae, forests, etc.) This doesn't mean it is sequestered. The algae can die and ferment and forests can burn, releasing CO2 back to atmosphere.
Earth has ability to very quickly bind large amounts of CO2 from atmosphere, true.
But it does not have ability to sequester it, because as long as the carbon is present in biomass, that biomass can burn or rot and change to methane/CO2.
Current coal, oil and gas deposits are due to the fact that at early stages of evolution there was no bacteria that could process some parts of biomass. For example, plants rather than rot would just be covered with more plants and become coal deposits.
Today, it is not possible to form new coal or oil deposits, because any biomass would be quickly digested/fermented/rotted before it could be sequestered.
Have you ever been in a coal mine?
Coal deposits can be very thick and can consist of practically pure coal with very little anything else.
Our densest forests if suddenly "pushed" (I guess covered by ash or anything else, without loosing carbon) would be millimeters in width.
(Not my area of expertise.)
Yes I've been in a coal mine. What a strange stat check.
There is a huge amount of sequestered carbon in such landforms. I don't know how that compares with primordial carbon formations.
One factor that seems to have been significant in the formation of the coal belt that runs from the present-day Czech republic through Germany, France, northern Spain, England, and the Apallachians is that this was a region of forest and/or swampland adjacent to mountains (the Appalachians, which are literally older than dirt), with the swamps sinking rapidly into a shallow seabed. That may also have played a major role in depriving the biomass of oxygen which would permit it to rot.
My own rampant speculation: even given decomposers capable of breaking down woody plant tissue, it's possible that these were insufficiently numerous, or inefficient, or otherwise limited, in ways that aren't currently relevant, such that decomposition is more efficient and rapid today.
Interesting questions. Unlikely to be answered by any of us here soon.